Raw materials are usually stored in the form of particles in silos, such as the food, chemical, and pharmaceutical field. The motion of granular materials can vary greatly in the flow of gases and liquids, due to their discrete particle aggregates. It is difficult to accurately explain using traditional theories, such as solid or fluid mechanics, and condensed matter physics. Particularly, the silo can serve as one of the most important carriers to store the particulate matter. It is still lacking in a comprehensive unified theory for the silo subjected to complex forces. Among them, the irregularity of rice seeds has a significant impact on the unloading in the silo, due to the nature of loose particles. Therefore, it is of great significance to clarify the impact of rice seed discharge flow in the silo. Auxiliary devices can also be added to transform the central into the overall flow bin. Simple and effective fluid modification can be used to adjust the structure of silos for the better particle flow. This study aims to explore the impact mechanism of different fluid modifications on the flow of rice seed particles during discharge in the silo. The transformation of the population flow pattern was achieved from the central to the overall flow for better population flow. The discrete element method (DEM) was selected to construct the traditional silo, vertical disturbance, and horizontal disturbance silo models. Rice seed particle models were established for the discharge simulation. The flow pattern was compared with the actual discharge experiment in the silo. A series of experiments was also conducted to verify the accuracy of the discrete element model and numerical simulation. The mass flow index (MFI) and z-axis particle velocity indicated that the particle velocity in the central region of traditional and vertically disturbed silos decreased with the increase of particle stacking height, whereas, the particle velocity increased in the sidewall region. There was a decrease in the particle velocity in the sidewall area of the horizontally disturbed silo, as the particle stacking height increased, whereas, the particle velocity increased in the central area. Traditionally, the conversion heights of the flow pattern were 130, 118, and 130 mm, respectively, in the vertically and horizontally disturbed silos. There was a variation in the vertical, horizontal, and angular velocity in the different areas of the silo. Specifically, the vertical velocity of the population decreased by 34.82% and 83.46%, respectively, compared with the traditional flow area of the silo under the action of the vertical and horizontal fluid. The fluctuation of population horizontal velocity increased, as the height of particle accumulation decreased in the silo population. The standard deviations of particle horizontal velocity were 0.027 3, 0.018 7, and 0.010 3, respectively, in the traditional silos, vertical and horizontal disturbance silos. There were similar changes in the particle angular velocity in the center and sidewall areas of traditional and vertical disturbance silos. The peak angular velocity was smaller in the center area of vertical disturbance silos, compared with the traditional silos. The variation of particle angular velocity was similar to the traditional silo in the flow area of a horizontal disturbance. But there was a small variation of particle angular velocity in a horizontal disturbance silo. The finding can provide the theoretical reference for the fluid design standards, structural and positional parameters, particularly for the high available area of the silo.

Cassava cultivation is low-cost and high-yielding, and tubers, stems and leaves can be widely utilized in the food medicine and light industry. However, cassava planting is mainly manual work at present. There is an urgent need to develop precision planting machines suitable for the agronomic requirements of cassava planting. A seeder is the core component of a precision planting machine, including the real-time and pre-cut seed-cutting type. Among them, the real-time seed cutting cannot realize the automatic sowing, due to the long and complicated shape of the cassava seed rods, while the low persistence of manual seed feeding and serious leakage. A seed cutter can be used to cut the cassava seed stems into seed stems of about 150 mm in length in pre-cut seeding. An automatic continuous and controlled seeding of cassava seed stems can be achieved through the seed discharge mechanism after cleaning. The lifting type seed rower has been improved to add the gravity seed cleaning mechanism, while the structure of the clamping plate has been optimized for the seed rowing effect. But the leakage filling still exists so far. Some research has been conducted on the seeders, such as slotted wheels, and single roller types. However, it is very necessary to improve the seed filling performance and qualification index, when seeding cassava seed stems with the existing pre-cut seed sower, because the cassava seed stems are cylindrical woody stalks of a certain length with surfaces of complex physical characteristics. Particularly, the performance of cassava precision seeding needs to be improved, due to a complex process with the multi-factor change. This study aims to improve the seed filling effect and low qualification index of pre-cut seeding type cassava precision seeder. A precision cassava seeding mechanism was designed with pre-cut seeding and friction belt, consisting of seed drop slide, active roller, type hole friction belt, support roller group, driven roller, and seed storage box. The basic structure and working principle of the seed-rowing mechanism were described to determine the parameters of key components. The main factors were then determined with the seed-filling performance of the seeding mechanism, according to the shape, number, installation inclination, and speed of the typed hole on the friction belt, as well as the thickness of the seed stem layer. The discrete element method (DEM) was used to establish a simulation model of the "seed stem group-hole friction zone". The single-factor simulation was realized to clarify the influence of each factor on the seed-filling performance. The optimal combination of factors and parameters was determined after quadratic regression and orthogonal rotational simulation. Taking the installation inclination angle of the seeding hole friction zone, the thickness of the seeding stem layer, and the speed of the seeding hole friction zone as the factors, the mathematical regression model of each factor was established for the evaluation index. The results showed that the influencing factors of the seed filling index and the leakage index were ranked in descending order of the speed of the type hole friction belt, the installation angle of the type hole friction belt, and the thickness of the seed stem layer. The optimal combination of factors and parameters was achieved in the bench test. The seed filling qualification index was 94.13% for the precut cassava-type friction belt precision seeding mechanism, and the leakage index was 3.77% when the thickness of the seed stem layer was rounded to 220-280 mm, the speed of the friction belt was 0.6 m/s, the installation inclination of the friction belt was 45°, the shape of the friction belt was C-shaped and the number of holes was 12. A better performance was achieved, where the seed filling index and the leakage index were 94.13% and 3.77%, respectively. The finding can provide a theoretical reference for the development of cassava precision seeders.

A particle system can often be required to analyze the interaction between rice seeds and agricultural machinery components in agricultural engineering, especially in precision rice sowing, efficient harvesting, and grain storage and transportation. The discrete element method (DEM) has been widely used to optimize the component parameters and operational performance. However, the long computation time of the DEM is confined to the rice seed systems, due to the irregular shape of the rice seeds in practical engineering. Ordinary computer hardware cannot fully meet the large-scale requirements of computation. Currently, the maximum number of particles in DEM can reach tens of millions, while the thousands of trillions are usually observed in actual agricultural engineering. Therefore, it cannot meet the simulation requirements of actual engineering, even with the computer accelerators. The significant challenge can remain to simulate the rice seed particle systems at the large-scale of agricultural engineering. Existing coarsening is also limited for the applicability of the DEM. This study aims to simulate the large-scale rice seed particle systems using precise scaling and coarsening in the DEM. The simulation efficiency was also improved to verify the effectiveness. The scaling relationship of the physical quantities was then derived for the precise scaling systems using dimensional analysis. The representative volume units were used to establish an approximate conservation relationship of the mass and momentum between coarse-grained and original systems at macroscopic and microscopic scales. The hybrid rice variety, Taixiang 812 (with a real grain size of 2.76 mm) was taken as the research object. The angle of repose was used as the experimental indicator. Three sets were applied as the target variables, including the internal collapse unloading and stacking, side wall collapse, and bottomless cylindrical stacking of the rice seeds. Seven scaling factors (1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0) were selected for the simulation, corresponding to a grain size range of 2.76~11.04 mm. A comparison was also made with the real experiment. The results show that there was some increase in the relative errors between the simulated and the experimental values from the three sets of test angles of repose, as the particle size of the rice seeds increased. When the particle size of the rice seeds was 2.76 mm, the relative errors of the three sets were 5.35%, 3.01%, and 2.92%, respectively, indicating an acceptable range. When the grain size of the rice seeds was 2.76 and 5.52 mm (the scaling factors of 1 and 2), the computational efficiency was reduced from 35.00 and 24.70 h to 11.67 and 3.61 h, compared with the variable proportion generalized coarsening. The large-scale rice seed particle systems can be expected to improve the computational efficiency and the accuracy of the simulation using precise scaling and coarsening in the DEM. The finding can also provide a theoretical basis for the large-scale particle systems at the engineering scale.

The particle flow is often required during the unloading of rice seeds from a conical hopper. In this study, a discrete element model (DEM) was established for the "conical hopper-rice seeds" system. A systematic investigation was implemented to examine the translational and rotational mechanical behaviors of the rice seeds within the hopper feeding zone. Key parameters were then quantified during discharge, including the seed orientation, internal granular pressure, and blockage probability. Ultimately, the simulation was carried out to reveal the relationship between granular flow rate at the discharge gate and the probability of blockage occurrence. The results demonstrate that the static lateral pressure from the rice seeds increased with the increasing depth from the material surface within the hopper. Notably, a sharp rise in the lateral pressure was observed specifically within the transition zone between the feeding and the discharge area. Furthermore, the peak dynamic lateral pressure by the rice seed particles on the hopper wall was consistently exceeded the static lateral pressure at the same height in the initiation of unloading. There was an increasing trend with the greater depth from the material surface. The particle motion revealed that the translational velocity of the rice seed particles displayed a radial distribution symmetric about the hopper axis. Axially, there was a significant increase in the translational velocity, as the flow was shifted from the near-wall region towards the central flow channel. The rotational velocity of the rice seed particles reached its maximum at the discharge outlet, and then diminished progressively upwards. Within the mass flow zone, the rotational velocity near the wall was slightly lower than that observed in the central region. Axially, the rotational velocity also followed an exponential distribution relative to the discharge height, except for the immediate wall region. A relatively high rolling contribution rate for the rice seed particles was the discharge gate and the near-wall zones of the hopper. The relative tangential velocity from the particle rotation was constituted a significant proportion of the total motion in these critical areas. In particle orientation, the seeds in the upper feeding zone were predominantly adopted a near-horizontal alignment. There was the noticeable reorientation, as the particle mass descended to the critical height. Specifically, the particle orientation gradually shifted towards a near-vertical alignment within the middle section of the hopper. As such, the orientation vectors of the surrounding particles progressively pointed either towards or away from the hopper axis during discharge. Crucially, there was the significant relationship between flow rate and the probability of blockage at the hopper discharge gate. Therefore, an "upward convex" arch was selected to calculate the theoretical blockage probability under the identical silo discharge gate width and silo charging port width. While a "non-upward convex" arch was selected to simulate the blockage probability. The calculated values shared the significantly closer agreement with the simulation as the assumed failure mechanism. The silo charging port width was used to enlarge the flow rate. There was an inverse correlation with the blockage probability. Once the flow rate reached more than 31.78 g/s (corresponding to a silo charging port width less than 41 mm), the discrepancy between theoretical and simulated blockage probabilities diminished to less than 0.3%. The theoretical blockage probability was derived from a random walk model, in order to accurately predict the simulated values over the tested range. These findings can provide the theoretical guidance for the practical material handling and storage, particularly in the hopper structural parameters for the high operational efficiency and reliability, like the cone angle and outlet size. The insights can offer the valuable references to mitigate the flow obstruction during grain handling and processing in conical hopper.